Question 1

The image above shows two point charges, $$q_1$$ and $$q_2$$, separated by a distance $$r. $$According to Coulomb's law, what is the magnitude of the force between them?

Accepted Answer

$$F = k \frac{q_1$ q_2$}{r^2$}$$

Question 2

If $$q_1 is $$positive and $$q_2 is $$negative, what is the direction of the force on $$q_1$$ due to $$q_2$$?

Accepted Answer

Toward $$q_2$$

Question 3

Suppose $$q_1 = 2$$ \ \mu	ext{C}$$, q_2$ = -3 \ \mu	ext{C}$$, and $$r = 0.5 \ 	ext{m}. $$What is the magnitude of the force between them? (Use $$k = 8.99 	imes 10^9$ \ 	ext{N} \cdot 	ext{m}^2/	ext{C}^2)$$

Accepted Answer

$$F = 0.216 \ 	ext{N}$$

Question 4

If the distance $$r$$ between the two charges in the image is doubled, how does the magnitude of the force change?

Accepted Answer

It becomes one-fourth as large

Question 5

Which of the following statements about the electric field created by $$q_1 at $$the location of $$q_2 is $$correct?

Accepted Answer

$$E = k \frac{q_1$}{r^2$}$$, directed away from $$q_1 if$$ $$q_1 is $$positive

Question 6

If a third charge $$q_3 is $$placed exactly midway between $$q_1$$ and $$q_2 ($$with $$q_1$$ positive and $$q_2$$ negative, equal in magnitude), what is the direction of the net electric field at the position of $$q_3$$?

Accepted Answer

Toward $$q_2$$

Question 7

Which of the following best describes the superposition principle as it applies to the forces on $$q_1 in $$the image above if more charges are added?

Accepted Answer

The net force on $$q_1 is $$the vector sum of the forces exerted by all other charges

Question 8

If both $$q_1$$ and $$q_2$$ are doubled in magnitude, how does the force between them change?

Accepted Answer

It becomes four times as large

Question 9

Which of the following is a correct statement about the direction of the electric field at a point on the line joining $$q_1$$ and $$q_2$$?

Accepted Answer

The electric field points away from positive charges and toward negative charges

Question 10

If $$q_1 is a $$conductor and $$q_2 is $$brought close to it, what happens to the charges in $$q_1$$?

Accepted Answer

Charges in $$q_1$$ redistribute so that the side closer to $$q_2$$ has an induced charge of opposite sign

Electric Charge and Electric Field – Study Notes

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